Hydrogen Migration In Phosphorous Doped Polycrystalline Silicon

1998 ◽  
Vol 513 ◽  
Author(s):  
N. H. Nickel ◽  
I. Kaiser
Keyword(s):  
Activation Energy ◽  
Polycrystalline Silicon ◽  
Hydrogen Diffusion ◽  
Chemical Potential ◽  
Effective Diffusion ◽  
High Hydrogen ◽  
Deep Traps ◽  
Level Model ◽  
Increasing Temperature ◽  
Two Level Model

ABSTRACTHydrogen diffusion in phosphorous doped polycrystalline silicon was investigated by deuterium diffusion experiments. The presence of phosphorous enhances hydrogen diffusion. For high hydrogen concentrations the activation energy of the effective diffusion-coefficient amounts to 0.25-0.35 eV. At low hydrogen concentrations diffusion is governed by deep traps that are present in an appreciable concentration of 6×108 - 1019 cm−3. The hydrogen chemical-potential, 9H, decreases with increasing temperature at a rate of ˜ 0.002 eV/K. The data are discussed in terms of a two-level model used to describe hydrogen diffusion in amorphous and undoped polycrystalline silicon.

Trap Dominated Hydrogen Transport in Disordered Silicon

1996 ◽  
Vol 420 ◽  
Author(s):  
N. H. Nickel ◽  
W. B. Jackson ◽  
J. Walker
Keyword(s):  
Solid State ◽  
Amorphous Silicon ◽  
Polycrystalline Silicon ◽  
Chemical Potential ◽  
Energy Difference ◽  
Hydrogen Transport ◽  
Hydrogen Trapping ◽  
Remote Plasma ◽  
Level Model ◽  
Two Level Model

AbstractHydrogen transport in polycrystalline silicon was investigated by deuterium diffusion experiments. D was introduced either from a remote plasma or a solid-state source. The data can be explained by a two-level model used to explain diffusion in amorphous silicon. The energy difference between transport level and deuterium chemical potential was found to be 1.3 eV. A band of shallow levels for hydrogen trapping is located about 0.6 eV below the transport level, while deep levels are about 1.7 eV below.

scholarly journals Modeling and thermodynamic properties of ‘bacaba’ pulp drying

2019 ◽  
Vol 23 (9) ◽  
pp. 702-708 ◽  
Author(s):  
Maria F. de Morais ◽  
José R. O. dos Santos ◽  
Marisângela P. dos Santos ◽  
Dyego da C. Santos ◽  
Tiago N. da Costa ◽  
...  
Keyword(s):  
Activation Energy ◽  
Thermodynamic Properties ◽  
Diffusion Coefficients ◽  
Effective Diffusion ◽  
Thermal Conditions ◽  
Drying Process ◽  
Experimental Conditions ◽  
Effective Diffusion Coefficients ◽  
Drying Rates ◽  
Increasing Temperature

ABSTRACT This study aimed to dry ‘bacaba’ (Oenocarpus bacaba Mart.) pulp under different thermal conditions, fit different mathematical models to the dehydration curves, and calculate the diffusion coefficients, activation energy and thermodynamic properties of the process. ‘Bacaba’ fruits were meshed to obtain the pulp, which was dried at temperatures of 40, 50 and 60 °C and with thickness of 1.0 cm. Increase in drying temperature reduced the dehydration times, as well as the equilibrium moisture contents, and drying rates of 0.65, 1.04 and 1.25 kg kg min-1 were recorded at the beginning of the process for temperatures of 40, 50 and 60 °C, respectively. The Midilli’s equation was selected as the most appropriate to predict the drying phenomenon, showing the highest R2, lowest values of mean square deviation (MSD) and χ2 under most thermal conditions, and random distribution of residuals under all experimental conditions. The effective diffusion coefficients increased with increasing temperature, with magnitudes of the order of 10-9 m2 s-1, being satisfactorily described by the Arrhenius equation, which showed activation energy (Ea) of 37.01 kJ mol-1. The drying process was characterized as endergonic, in which enthalpy (ΔH) and entropy (ΔS) reduced with the increment of temperature, while Gibbs free energy (ΔG) was increased.

scholarly journals Effect of Microstructure on Hydrogen Permeation in EA4T and 30CrNiMoV12 Railway Axle Steels

Metals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 164 ◽  
Author(s):  
Tingzhi Si ◽  
Yunpeng Liu ◽  
Qingan Zhang ◽  
Dongming Liu ◽  
Yongtao Li
Keyword(s):  
Activation Energy ◽  
Hydrogen Diffusion ◽  
Hydrogen Permeation ◽  
Martensitic Structure ◽  
Hydrogen Diffusivity ◽  
High Hydrogen ◽  
Railway Axle ◽  
Effective Hydrogen ◽  
Trapping Sites ◽  
Effect Of Microstructure

A comparative study was conducted to reveal the effect of microstructure on hydrogen permeation in the EA4T and 30CrNiMoV12 railway axle steels. Unlike the EA4T with its sorbite structure, 30CrNiMoV12 steel shows a typical tempered martensitic structure, in which a large number of fine, short, rod-like, and spherical carbides are uniformly dispersed at boundaries and inside laths. More importantly, this structure possesses plentifully strong hydrogen traps, such as nanosized Cr7C3, Mo2C, VC, and V4C3, thus resulting in a high density of trapping sites (N = 1.17 × 1022 cm−3). The hydrogen permeation experiments further demonstrated that, compared to EA4T, the 30CrNiMoV12 steel not only delivered minimally effective hydrogen diffusivity but also had a high hydrogen concentration. The activation energy for hydrogen diffusion of the 30CrNiMoV12 steel was greatly increased from 23.27 ± 1.94 of EA4T to 47.82 ± 2.14 kJ mol−1.

Hydrogen Transport in Phosphorus and Boron Dopedpolycrystalline Silicon

1999 ◽  
Vol 557 ◽  
Author(s):  
N. H. Nickel ◽  
I. Kaiser
Keyword(s):  
Polycrystalline Silicon ◽  
Hydrogen Diffusion ◽  
Effective Diffusion ◽  
Single Crystal Silicon ◽  
Hydrogen Transport ◽  
Crystal Silicon ◽  
Thermally Activated ◽  
Boron Doped ◽  
Similar Dependence ◽  
Formation Energies

AbstractHydrogen diffusion in phosphorus and boron doped polycrystalline silicon was investigated by deuterium diffusion experiments. The presence of dopants enhances hydrogen diffusion. The effective diffusion coefficient Deff is thermally activated and the activation energy varies between 0.1 and 0.4 eV. This is accompanied by a variation of the diffusion prefactor by 12 orders of magnitude. Using the theoretical diffusion prefactor the actual energy EA was calculated from Deff.EA also depends strongly on the Fermi energy and exhibits a similar dependence as the formation energies of H+ and H- in single crystal silicon.

scholarly journals Statistical study of thermoradiative and photovoltaic cells based on a two-level model

2021 ◽  
Author(s):  
J. J. Fernández
Keyword(s):  
Statistical Study ◽  
Open Circuit Voltage ◽  
Chemical Potential ◽  
Photovoltaic Cells ◽  
Open Circuit ◽  
Energy Model ◽  
Conversion Process ◽  
Level Energy ◽  
Level Model ◽  
Two Level Model

AbstractWe use a two-level energy model to understand the conversion process that takes place in thermoradiative cells and to compare it with the conversion process that happens in photovoltaic cells. In this way, we show that in both kinds of converters the conversion process can be studied as the succession of a change in the populations of the levels that occur at constant chemical potential and a change in the value of the chemical potential of the two levels that happens while keeping their populations constant. As an application of the model, we will discuss why in thermoradiative cells the open-circuit voltage is negative while it is positive in photovoltaic cells. We also show that the expression for the open-circuit voltage is the same in both kinds of cells but that due to the values of the temperatures it is negative in thermoradiative cells and positive in photovoltaic ones.

Silicon-Hydrogen Bonding and Hydrogen Diffusion in Amorphous Silicon

1995 ◽  
Vol 377 ◽  
Author(s):  
Chris G. Van De Walle ◽  
R. A. Street
Keyword(s):  
Activation Energy ◽  
Amorphous Silicon ◽  
First Principles ◽  
Density Functional ◽  
Hydrogen Diffusion ◽  
Chemical Potential ◽  
Energy Levels ◽  
Diffusion Activation Energy ◽  
Quantitative Identification ◽  
Diffusion Activation

ABSTRACTDespite its importance for technological applications, the behavior of hydrogen in amorphous silicon is not fully understood. In particular, the anomalously low activation energy (1.5 eV) for hydrogen diffusion has remained unexplained. We investigate the interaction of hydrogen with dangling bonds using first-principles pseudopotential-density-functional calculations. Our analysis shows that the diffusion activation energy should be measured from the hydrogen chemical potential, and that this level should be identified with the formation energy of Si-H bonds. A quantitative identification of the energy levels with experimental observables is then possible.

Two Level Model of Hydrogen Diffusion in Nanoporous Solids with Strongly Bound Adsorption States

2015 ◽  
Vol 119 (13) ◽  
pp. 7234-7242
Author(s):  
Carlos Rodríguez-Castellanos ◽  
Javier Q. Toledo-Marín
Keyword(s):  
Hydrogen Diffusion ◽  
Level Model ◽  
Nanoporous Solids ◽  
Two Level Model

scholarly journals Tagasaste, leucaena and paulownia: three industrial crops for energy and hemicelluloses production

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Alberto Palma ◽  
Javier Mauricio Loaiza ◽  
Manuel J. Díaz ◽  
Juan Carlos García ◽  
Inmaculada Giráldez ◽  
...  
Keyword(s):  
Activation Energy ◽  
Acid Hydrolysis ◽  
Energy Production ◽  
Combustion Process ◽  
Operating Conditions ◽  
Raw Material ◽  
Energy Of Combustion ◽  
Increasing Temperature ◽  
Hydrolysis Of ◽  
Chamaecytisus Proliferus

Abstract Background Burning fast-growing trees for energy production can be an effective alternative to coal combustion. Thus, lignocellulosic material, which can be used to obtain chemicals with a high added value, is highly abundant, easily renewed and usually inexpensive. In this work, hemicellulose extraction by acid hydrolysis of plant biomass from three different crops (Chamaecytisus proliferus, Leucaena diversifolia and Paulownia trihybrid) was modelled and the resulting solid residues were used for energy production. Results The influence of the nature of the lignocellulosic raw material and the operating conditions used to extract the hemicellulose fraction on the heat capacity and activation energy of the subsequent combustion process was examined. The heat power and the activation energy of the combustion process were found to depend markedly on the hemicellulose content of the raw material. Thus, a low content in hemicelluloses resulted in a lower increased energy yield after acid hydrolysis stage. The process was also influenced by the operating conditions of the acid hydrolysis treatment, which increased the gross calorific value (GCV) of the solid residue by 0.6–9.7% relative to the starting material. In addition, the activation energy of combustion of the acid hydrolysis residues from Chamaecytisus proliferus (Tagasaste) and Paulownia trihybrid (Paulownia) was considerably lower than that for the starting materials, the difference increasing with increasing degree of conversion as well as with increasing temperature and acid concentration in the acid hydrolysis. The activation energy of combustion of the solid residues from acid hydrolysis of tagasaste and paulownia decreased markedly with increasing degree of conversion, and also with increasing temperature and acid concentration in the acid hydrolysis treatment. No similar trend was observed in Leucaena diversifolia (Leucaena) owing to its low content in hemicelluloses. Conclusions Acid hydrolysis of tagasaste, leucaena and paulownia provided a valorizable liquor containing a large amount of hemicelluloses and a solid residue with an increased heat power amenable to efficient valorization by combustion. There are many potential applications of the hemicelluloses-rich and lignin-rich fraction, for example as multi-components of bio-based feedstocks for 3D printing, for energy and other value-added chemicals.

scholarly journals Kinetics and thermodynamic properties related to the drying of 'Cabacinha' pepper fruits

2016 ◽  
Vol 20 (2) ◽  
pp. 174-180 ◽  
Author(s):  
Hellismar W. da Silva ◽  
Renato S. Rodovalho ◽  
Marya F. Velasco ◽  
Camila F. Silva ◽  
Luís S. R. Vale
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Free Energy ◽  
Thermodynamic Properties ◽  
Gibbs Free Energy ◽  
Removal Rate ◽  
Effective Diffusion ◽  
Drying Time ◽  
Three Samples ◽  
Different Temperatures

ABSTRACT The objective of this study was to determine and model the drying kinetics of 'Cabacinha' pepper fruits at different temperatures of the drying air, as well as obtain the thermodynamic properties involved in the drying process of the product. Drying was carried out under controlled conductions of temperature (60, 70, 80, 90 and 100 °C) using three samples of 130 g of fruit, which were weighed periodically until constant mass. The experimental data were adjusted to different mathematical models often used in the representation of fruit drying. Effective diffusion coefficients, calculated from the mathematical model of liquid diffusion, were used to obtain activation energy, enthalpy, entropy and Gibbs free energy. The Midilli model showed the best fit to the experimental data of drying of 'Cabacinha' pepper fruits. The increase in drying temperature promoted an increase in water removal rate, effective diffusion coefficient and Gibbs free energy, besides a reduction in fruit drying time and in the values of entropy and enthalpy. The activation energy for the drying of pepper fruits was 36.09 kJ mol-1.

Sign in / Sign up

Export Citation Format

Share Document